I've heard there's some amazing hiking in the hills around HK, any specific trails or views we should trek to? We'll be there next week!
There are far more than you expect. Have a search for Dragon's Back on Hong Kong Island
Or catch the ferry to Lamma Island. You can walk across the island and the have a meal at one of the fish restaurant on the other side. They all run boats back to the island.
Do have a trip on the Star Ferry for me.
Go to Peak Road (funicular tram from Peak Tram), enjoy the view of the pollution from high up, then follow Lugard Road around Mount Davis which will give you views over Victoria Harbour, Lamma Island, and Aberdeen Harbor. There should be signs to Lugard Road from the Peak Viewing point. It's a nice short hike, not too strenuous.
I believe you can hike down to Aberdeen from there, if you feel like more exercise.
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For me, Sunset Peak is one of the most beautiful hiking trails in Hong Kong, it is in Lantau Island, it's beautiful, but it's a difficult one.
The absolute BEST one is quite hidden, but well worth the adventure. It's called Ping Nam Stream. I did a whole post on how to get there here: http://www.coffeewithasliceoflife.com/2015/07/02/the-most-beautiful-place-in-hong-kong/